The reduction of fault current is one of the oldest problems of power systems engineering. Fault current reduction permits the interconnection of large networks without replacing circuit breakers, improves transient stability, and reduces the cost of equipment. The paper investigates the reduction of fault current by the insertion of a resonant LC circuit into the transmission line. The device consists of a capacitor and a thyristor-switched inductance, tuned to the supply frequency. The thyristor switches are operated at zero-current-crossing to eliminate the generation of harmonics. The system operation is analysed using analytic methods and transient simulation techniques. A parametric study determines the effect of components and network parameters on the current limiter operation. Design methods and component selection criteria are developed. The results demonstrate that the device can reduce both transient and steady-state fault current significantly. It can be built with commercially available components. The significant operation improvement is expected to justify the cost of the new device.